The pilates is an interesting suggestion, I have heard many good things about it. Supposedly it builds your 'core' muscles around the pelvic area? When I used to do yoga (the light version not the human pretzel) it helped with the stretching and building thigh muscles. You feel a lot looser in the back and with the body feeling flexible there's less strain build up. Basically your body is not solid as a brick and you can actually bend your back!
Yes, Pilates helps to build core strength, not only in the pelvic area, but throughout the body and with an emphasis on improving alignment and breathing. It also improves flexibility and joint mobility and muscle endurance. And because it is a low impact form of exercise, the risk of injury is low and it is good for all ages. But anyone with existing problems should check their doctor first to see if it might be of benefit.
It is very important to find a good, qualified teacher. I've done it for years and years and there are a lot of classes on offer (mainly in leisure centres) that are very poor, doing the exercises incorrectly at too rapid a pace, which provides little or no benefit and may actually aggravate existing back problems. So if you are tempted to try it, take the time to seek out a good practitioner. Any teacher worth their salt will carry out a proper appraisal of your existing health and be able to say whether it would be suitable.
I'm fortunate that my Pilates teacher is a also qualified (paediatric) physiotherapist in her day job, which helps. All the exercises (some using resistance aids) are done very very slowly, with her adjusting you where necessary to ensure you are keeping your alignment. Classes are small, no more than 8 people, so the teacher can monitor and assist each person.
I also do yoga (gentle form) but find I get more lasting benefit from pilates, though last night's yoga session has helped ease out back stiffness I had as a result of my full on car detailing session last week to rid my car of the Sahara sand!
Anyway, hope that making some slight seat adjustments makes a difference to you and eases your GTI lumbar pain
